1. Field of the Invention
This invention relates to a cut sheet feeder for automatically feeding cut sheets and to a recording apparatus using the same.
2. Related Background Art
A cut sheet feeder is for automatically supplying cut sheets or the like to a recording apparatus, and it is a device which eliminates the operation of manually inserting sheets (recording mediums such as printing paper and plastic sheets), thereby improving the operability of the recording apparatus and mitigating the user's burden.
As cut sheet feeders of this type, use has widely been made of a device of the type which is not provided with its own drive source (a motor or the like) in its body and neither provided with an electrical output source indicative of its own presence (the state in which it is connected and usable), that is, a device of relatively low cost.
On the other hand, a recording apparatus such as a printer has various sheet conveying functions so as to correspond to various types of sheets (recording mediums) such as cut sheets, continuous paper, continuous paper adapted to be conveyed by a sprocket or the like (pin feed) and continuous paper adapted to be friction-fed by a friction roller or the like.
The user, when utilizing a recording apparatus, selects and uses a sheet conveying function corresponding to the type of sheets (recording mediums).
If the user commits a mistake in the selection, for example, commits an error of using the friction feed and the pin feed together, irregularity occurs in the sheet feeding pitch or sheet jam occurs.
The recording apparatus is designed such that when the user selects the pin feed, the friction roller or the like is retracted so that the other friction feed function does not affect the sheets.
Heretofore, design has been made such that when the cut sheet feeder is connected to the recording apparatus, the recording apparatus side is selected to the friction feed mode on the part of the user and a sheet fed from the feeder is nipped between friction rollers and directed into the recording apparatus. In such case, if the pin feed mode is selected, the sheet will not be introduced into the recording apparatus even if an effort is made to feed the sheet from the feeder into the recording apparatus.
The operation of selecting the friction feed and the pin feed has usually been accomplished by the change-over operation using a release lever or the like provided in the recording apparatus body.
In some recording apparatuses of high added value, even if the user does not manually move the release lever, power is obtained from a drive source such as a motor by a soft command or some selection signal to forcibly move the friction rollers back and forth, but such a construction has suffered from a problem that the cost becomes very high and the product becomes expensive.
From the fact that as previously described, when the cut sheet feeder is used, only the friction feed functions effectively and therefore the change-over of the release lever or the like is unnecessary and the fact that since the prior-art recording apparatus of this type is often personally used on a desk, the configuration and dimensions thereof are designed as compactly as possible, the release lever, etc. are often hidden in the interior of the feeder in a state in which the cut sheet feeder is placed on and connected to the recording apparatus.
There are devices in which the release lever, etc. are compulsorily disposed outside the feeder to enable the presence thereof to be readily confirmed, but they are not preferable in appearance.
On the other hand, it is often the case with devices in which the release lever is hidden in the interior of the feeder that the position of the release lever cannot be confirmed.
Therefore, when the user connects the feeder to the recording apparatus while forgetting to change over the feeder to the friction feed mode, abnormality is not noticed until trouble such as unsatisfactory feed occurs after the first sheet has been fed from the feeder, and the feeder must be removed and reset after it has been found that the cause of the trouble is the misoperation of the release lever, and this has meant a problem that handling becomes cumbersome.
Also, in a recording apparatus such as a printer, a facsimile apparatus or a typewriter, there is a case where a continuous sheet such as rolled paper or fan-folded paper is used as a recording medium such as printing paper or plastic sheet, and a case where cut sheets are used as such recording medium.
Generally, where a continuous sheet is used, it may be set only once and thereafter recording can be continuously effected thereon, and this is convenient to the user, while in the case of cut sheets, they must be manually set one by one, and this has led to an inconvenience that the cut sheets must be always monitored, which has also meant low efficiency of office work.
Usually, a recording apparatus is provided with a sheet feeding knob for manually rotating a sheet feed roller when manually setting cut sheets. Accordingly, the work of manually setting cut sheets one by one has been done in the procedures of inserting a sheet from the sheet insertion port of the recording apparatus and pushing it into a location at which it contacts the peripheral surface of the sheet feed roller (usually a portion against which the pinch roller is urged), and thereafter manually operating the sheet feeding knob to rotate the sheet feed roller by a suitable angle, thereby setting the sheet at a desired leading position.
Referring to FIG. 1 of the accompanying drawings which shows an example of the recording apparatus of this type, a sheet feeding knob 1 is mounted in a half-embedded state in which it is incorporated into the recording apparatus body and partly protrudes from the upper surface of a case 2.
Referring now to FIG. 2 of the accompanying drawings which shows another example of the recording apparatus having a sheet feeding knob, the sheet feeding knob 3 is mounted in a state in which it is exposed out of the case 4 of the recording apparatus so as to be able to be grasped by a hand.
The sheet feeding knobs 1 and 3 of FIGS. 1 and 2, respectively, are directed only to the manual feeding of sheets and therefore, shallow grooves for anti-slippage are merely provided on the peripheral surface thereof. These shallow grooves are formed in such a manner that the user does not feel any pain when he or she touches the knob, and usually are at a thin pitch.
Particularly, in the case of the half-embedded type sheet feeding knob 1 of FIG. 1, as compared with a knob which can be grasped over the full periphery (for example, the knob 3 of FIG. 2), the peripheral surface thereof is pushed and rotated by a fingertip and thus a considerable force is applied to the fingertip and accordingly, more consideration has been given so as to prevent the fingertip from feeling pain.
On the other hand, in order to give up manually feeding sheets and improve the usability when cut sheets are used, means is adopted for placing a cut sheet feeder as an option on a recording apparatus and connecting it to the latter for operative association therewith, and making it possible to automatically feed and discharge the cut sheets one by one.
Such cut sheet feeder may be divided broadly into the type in which the feeder itself is equipped with its drive source depending on the degree of requirement and the capability of a recording apparatus and the type which is always under the control of a recording apparatus and in which the driving power is provided from the recording apparatus.
Further, with regard to the latter type, there have been proposed a device in which a gear exclusively for use as transmission means for driving the feeder is particularly provided in the recording apparatus, a device in which power is obtained from rotation of the sheet feed roller of the recording apparatus by a friction force, and a device in which, from the viewpoints of space and arrangement, power is obtained through a sheet feeding knob for manually rotating the sheet feed roller of the recording apparatus.
Where the drive force of the cut sheet feeder is transmitted through the sheet feeding knob as previously described, a gear is formed on the outer periphery of the sheet feeding knob and this gear is brought into meshing engagement with a gear in the feeder, whereby transmission of power is accomplished.
FIGS. 3 and 4 of the accompanying drawings illustratively show conventional sheet feeding knobs serving also as the power transmitting gear.
In the sheet feeding knob 5 of FIG. 3, it has been necessary to satisfy the following conditions in order to realize the function of a manually operated knob for the sheet feed roller and the function of a power transmitting gear on the same outer peripheral surface:
(i) The outer diameter of a gear 6 becomes greater to keep the co-usability thereof with the sheet feeding knob 5;
(ii) Reliable meshing engagement is necessary and the tooth form of the gear 6 becomes larger to secure the ease of mounting and dismounting; and
(iii) Because the knob is rotated by fingers, the axial dimensions thereof are necessary and the width thereof becomes greater.
To satisfy these conditions, in the conventional sheet feeding knob as shown in FIG. 3, the gear 6 of large tooth form has been formed on the full outer periphery of the knob, and this has led to a problem that even if the tooth tops and end portion are endowed with a curvature, fingers can feel great pain when they operate the knob.
So, in order to mitigate the pain of the fingers, there has been adopted a construction as shown in FIG. 4 wherein the sheet feeding knob 7 is axially thick (great in width) and the gear portion 8 meshing with the gear of the cut sheet feeder and the knob portion 9 to be touched by the user (the portion to be touched by fingers) are formed separately from each other, or a construction in which the width of the gear portion 8 meshing with the gear of the cut sheet feeder is minimized and most of the knob is the knob portion 9.
However, in the sheet feeding knob 7 of great width, there have arisen problems in appearance and interchangeability (co-usability) and moreover, there has arisen a problem that the necessary space is large and the merit of utilizing the sheet feeding knob to transmit the drive force is eliminated and the difference from a case when a discrete transmission path is provided becomes small.
Also, in the construction wherein the width of the gear portion 8 is minimized, there have arisen problems in the mountability and dismountability thereof and the strength of the gear.
In addition, thick-walled portions are present adjacent to the portion such as the gear portion 8 which requires accuracy and therefore, there has arisen the problem of thinning when the knob is shaped in a mold, which has also led to a problem that accuracy cannot be maintained.